.calc {
    width: 234px;
    border: 1px solid #000;
    border-radius: 10px;
    overflow: hidden;
}

.calc .calc-screen {
    width: 100%;
    height: 80px;
    line-height: 80px;
    padding: 0 10px;
    color: #fff;
    background-color: #262526;
    font-size: 35px;
    text-align: right;
}

.calc button {
    background-color: #5e5e5e;
    display: inline-block;
    width: 25%;
    height: 50px;
    line-height: 50px;
    text-align: center;
    font-size: 24px;
    border-color: #000;
    border-style: solid;
    border-width: 0 1px 1px 0;
    color: #fff;
    cursor: pointer;
}

.calc button:active {
    background-color: #7e7e7e;
}

/* 0 */
.calc button.zero {
    width: 50%;
}

/* 控制的按钮的颜色 */
.calc button.ctrl {
    background-color: #3e3f3e;
}

.calc button.ctrl:active {
    background-color: #6f706f;
}

/* 运算的按钮颜色 */
.calc button.exp {
    background-color: #fd8d0e;
}

.calc button.exp:active {
    background-color: #f5b974;

}